A sperm granuloma is a lump of extravasate sperm that appears along the vasa deferentia or epididymides in vasectomized men. Sperm granulomas are rounded or irregular in shape, one millimeter to one centimeter or more, with a central mass of degenerating sperm surrounded by tissue containing blood vessels and immune system cells. Sperm granulomas can be either asymptomatic or symptomatic, i.e. painful. Sperm granulomas are present in the vast majority of vasectomized men as a result of the pressure-induced changes of vasectomy.